US5765183A - Disk array subsystem and data generation method therefor - Google Patents

Disk array subsystem and data generation method therefor Download PDF

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Publication number
US5765183A
US5765183A US08/524,705 US52470595A US5765183A US 5765183 A US5765183 A US 5765183A US 52470595 A US52470595 A US 52470595A US 5765183 A US5765183 A US 5765183A
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data
storage means
disk storage
parity
magnetic disk
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US08/524,705
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Akira Kojima
Akihito Ogino
Soichi Isono
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Hitachi Ltd
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Hitachi Ltd
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Assigned to HITACHI, LTD. reassignment HITACHI, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ISONO, SOICHI, KOJIMA, AKIRA, OGINO, AKIHITO
Priority to US08/975,503 priority Critical patent/US5875460A/en
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F11/00—Error detection; Error correction; Monitoring
    • G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
    • G06F11/08—Error detection or correction by redundancy in data representation, e.g. by using checking codes
    • G06F11/10—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
    • G06F11/1076—Parity data used in redundant arrays of independent storages, e.g. in RAID systems
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/18—Error detection or correction; Testing, e.g. of drop-outs
    • G11B20/1833—Error detection or correction; Testing, e.g. of drop-outs by adding special lists or symbols to the coded information
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F11/00—Error detection; Error correction; Monitoring
    • G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
    • G06F11/08—Error detection or correction by redundancy in data representation, e.g. by using checking codes
    • G06F11/10—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
    • G06F11/1008—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's in individual solid state devices
    • G06F11/1012—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's in individual solid state devices using codes or arrangements adapted for a specific type of error
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2211/00—Indexing scheme relating to details of data-processing equipment not covered by groups G06F3/00 - G06F13/00
    • G06F2211/10—Indexing scheme relating to G06F11/10
    • G06F2211/1002—Indexing scheme relating to G06F11/1076
    • G06F2211/1054—Parity-fast hardware, i.e. dedicated fast hardware for RAID systems with parity
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing

Definitions

  • the present invention relates to a disk array subsystem for connecting and operating a plurality of disk drives in parallel and a data generation method therefor and particularly to a disk array subsystem for realizing a reduction in a write penalty in RAID4 (redundant array of inexpensive disks) and RAID5.
  • RAID4 redundant array of inexpensive disks
  • a disk array subsystem is a magnetic disk drive for connecting and operating a plurality of inexpensive small disk drives in parallel so as to realize performance equivalent to that of a SLED (single large expensive disk).
  • a general arrangement of a disk array is shown in FIG. 7.
  • This disk array comprises a disk array controller 2 which is connected to a host computer 1 via a host interface 12 and a plurality of disk drives 18 which are connected to the disk array controller 2 and operate in parallel.
  • the disk array controller 2 comprises a host interface controller 3 for storing a read or write instruction from the host computer 1 once, a CPU 4 for controlling the operation of the disk array controller 2, a cache memory 6 for storing data transferred between the host computer 1 and the disk drives 18, a cache memory controller 5 for controlling the cache memory, and a disk controllers 7 for controlling data transfer between the disk array controller 2 and the disk drives 18.
  • the cache memory controller 5 When the cache memory controller 5 confirms at the time of reading that requested data exists in the cache memory 6, the data is transferred from the cache memory 6 to the host computer 1 via the host interface 12. When the requested data does not exist in the cache memory 6, the CPU 4 stores the data in the cache memory 6 from a disk drive 18 storing the data via the disk controller 7 and the cache memory controller 5. The cache memory controller 5 transfers the data to the host computer 1 after the storing ends or in parallel with the storing.
  • write data transferred from the host computer 1 is stored in the cache memory 6 by the cache memory controller 5 via the host interface 12 and the host interface controller 3.
  • the cache memory controller 5 writes the write data into the disk drive 18 designated by the CPU 4 via the disk controller 7 after the storing ends or in parallel with the storing.
  • the disk array subsystem generates parity on data stored on a plurality of data disks and stores it on a parity disk.
  • the parity disk is fixed in a special disk drive.
  • concentration on the parity disk the parity is distributed evenly to all the disk drives for each data.
  • U.S. Pat. No. 5,191,584 discloses a data updating method in a disk array subsystem of RAID4 or RAID5. According to this data updating method, when a disk array controller accesses one data disk by each processing unit, there is no need of accessing all the data disks, even when writing data.
  • the disk array controller calculates new parity data by the exclusive OR of the old data of the data disk for writing, the old parity data of the parity disk, and new data transferred from the host computer and updates the parity disk according to the new parity data. Therefore, another process can be executed for disks other than the data disk for writing and the parity disk. Particularly in RAID5, no parity disk is specified, so that the write process can be executed at the same time.
  • a problem caused by this method is that the five processes indicated below are generated because the parity disk is updated for writing data as shown in FIG. 8 and the processing capacity is lowered.
  • the four processes except 4) among the aforementioned five processes are accompanied by an access to disk drives process and it causes a performance reduction of the disk array subsystem.
  • This performance reduction due to increase in access to disk drives process for updating of the parity disk which occurs when writing data is called a write penalty.
  • a write penalty is called a write penalty.
  • pseudo-parity which works as follows. In case a plurality of disk drives is written by a new data, the corresponding new parity data, i.e., a parity data obtained by calculating the exclusive OR of the new data and the corresponding old data is called a pseudo-parity of the new data.
  • the pseudo-parity works as a new parity data which is common to all the plurality of the disk drives corresponding to the new data, and therefore is called a pseudo-parity.
  • An object of the present invention is to provide a disk array subsystem for preventing the performance from deteriorating even if the access process to a recording medium is increased by a write penalty for writing data, and a method therefor.
  • the disk array subsystem of the present invention comprising a plurality of magnetic disk storage means
  • at least one magnetic disk storage means among the above magnetic disk storage means acquires data (new data) to be written into one magnetic disk storage means among the above plurality of magnetic disk storage means, reads the data (old data) in its own magnetic disk storage means which corresponds to the new data, calculates the exclusive OR of the new data and the old data, generates the calculated data, and writes the calculated data in the corresponding address in its own magnetic disk storage means or transfers it to the upper apparatus or another magnetic disk storage means.
  • a disk drive employed in the disk array subsystem of the present invention has at least two interfaces.
  • the first interface connects the disk controller and a disk drive and the second interface connects a plurality of disk drives having common parity.
  • New data transferred from the host computer is transferred to a disk drive by the disk array controller.
  • the disk drive receives the new data by the first interface, reads the old data on the recording medium at the same time, calculates the exclusive OR of the new data and the old data, transfers the result from the second interface to the parity disk as pseudo-parity data, and writes the new data on the recording medium.
  • the disk drive in which the parity data of the new data is stored receives the pseudo-parity data via the second interface, reads the old parity data on the recording medium at the same time, calculates the exclusive OR of the pseudo-parity data and the old parity data, and writes the result on the recording medium as new parity data.
  • the present invention having the aforementioned structure, has the function and operation indicated below.
  • a disk drive executes a process for reading old data and old parity data for updating parity data of the disk array subsystem and a process for calculating and writing new parity data, so that the burden imposed on the disk array controller is lightened. Pseudo-parity data is transferred not via the disk array controller, so that a reduction in the processing capacity due to multiple simultaneous access to a disk drive from the disk controller can be prevented, and the efficiency and performance in writing data can be improved.
  • FIG. 1 is a block diagram of a disk array subsystem in an embodiment of the present invention.
  • FIG. 2 is a detailed block diagram of a disk drive in an embodiment of the present invention.
  • FIG. 3 is a block diagram of RAID4 in an embodiment of the present invention.
  • FIG. 4 is a time chart of the operation of RAID4 for writing in an embodiment of the present invention.
  • FIG. 5 is a block diagram of RAID5 in an embodiment of the present invention.
  • FIG. 6 is a time chart of the operation of RAID5 for writing in an embodiment of the present invention.
  • FIG. 7 is a block diagram of a conventional disk array subsystem
  • FIG. 8 is a time chart of data transfer of RAID5 for writing in a conventional example.
  • FIG. 1 shows an embodiment of the present invention.
  • a parity group comprises n data disk drives and one parity disk drive.
  • Each disk drive 8 has two interfaces. One of them is an interface 13 connected to the host computer via a disk controller 7. The other is an interface 14 for connecting disk drives constituting the parity group to each other.
  • the interface 13 is referred to as a disk interface and the interface 14 is referred to as a parity interface.
  • a disk drive 8 which receives a write instruction calculates the exclusive OR of new data transferred by the disk interface 13 and the old data on the disk medium and transfers the calculation result to the parity disk drive via the second interface.
  • the parity disk drive stores the exclusive OR of the calculation result and the old parity data stored in the disk drive as new parity data.
  • FIG. 2 shows a detailed block diagram of disk drive 8.
  • the disk drive 8 comprises a buffer memory 21 for storing data transferred from the disk interface 13 or the parity interface 14, a buffer memory 22 for storing data read from a recording medium, an arithmetic unit 23 for calculating the exclusive OR of output of the buffer memory 21 and output of the buffer memory 22, a switching unit 25 for switching the connection destination of the parity interface 14 or the disk interface 13, a switching unit 24 for switching the connection destination of the disk, interface controllers 28a and 28b between the host interface (HOST IF) and the parity interface 14 (PARITY IF), FIFO units 27a and 27b command interpreters 29a and 29b, and two data speed adjustment FIFO units 27a and 27b.
  • HOST IF host interface
  • PARITY IF parity interface 14
  • the buffer memories 21 and 22 have data speed adjustment FIFO units 30 and 31 for input and output.
  • the disk interface has a data speed adjustment FIFO unit 32 for input and output: The old data "old” is read from the disk drive, in correspondence with the inputting of new data and its exclusive OR(NEW/EOR) is calculated, and is supplied to FIFO unit 31, as shown in FIG. 2.
  • the buffer memory 21 stores the exclusive OR of the write data (new data) transferred from the disk interface 13 and the old data at the corresponding address which is read from the disk, and when the disk drive is a parity disk, the buffer memory 21 stores the exclusive OR of the pseudo-parity data transferred from the parity interface 14 and the old parity data at the corresponding address which is read from the disk.
  • the switching units 24 and 25 select EOR23 for a write penalty countermeasure of the RAID of the present invention. For executing normal read/write, they select OLD/NEW.
  • the buffer memory 22 stores the old data or old parity data of the recording medium 26.
  • the exclusive OR of the new data and old data is stored in the buffer memory 21, selected by the switching unit 25, and outputted to the parity interface 14.
  • the exclusive OR of the pseudo-parity data and old parity data is stored on the recording medium 26 as new parity data from the FIFO unit 32.
  • FIG. 3 shows an embodiment of the present invention and the arrangement in the case of RAID4.
  • the parity disks are fixed.
  • disk controllers are designated as 7-1, 7-2, 7-3, and 7-(n+1); as 8-21, 8-22,8-23, and 8-2(n+1) and as 8-m1, 8-m2, 8-m3, and 8-m(n+1).
  • Disk interfaces are designated 13-1, 13-2, 13-3, and 13(n+1) and parity interfaces as 14-1, 14-2, and 14-m.
  • the disk drives 8-1(n+1) to 8-m(n+1) are parity disks. 7-1, 7-2, . . .
  • 7-(n+1) are disk controllers corresponding to disk controllers 7 of FIG. 1, wherein 7-1 . . . 7-3 are controllers for data disks, and the 7-(n+1) controller is a parity disk controller.
  • 13-1 . . . 13-(n+1) are disk interfaces corresponding to parity interfaces 13 of FIG. 1.
  • 14-1 . . . 14-m are parity interfaces corresponding to parity interfaces 14 of FIG. 1.
  • 8-m1 . . . 8-m(n+1) are disk drives corresponding to disk drives 8 of FIG. 1.
  • FIG. 4 shows detailed processing of this embodiment.
  • the disk drive 8-11 which receives write data to address #0 from the disk controller 7-1 via the interface 13-1:
  • the parity disk drive 8-1(n+1) which receives the pseudo-parity from the data disk drive 8-11 via the interface 14-1:
  • FIG 5 shows another embodiment of the present invention in which the arrangement of the array of disk drives is a RAID5 arrangement.
  • the parity disks are not fixed and the n+1 data disks in each row of the array rotate for each data processing operation.
  • the other operations are the same as those in the case of RAID4. It is necessary for a data disk drive to recognize the corresponding parity disk among the disk drives so as to transfer pseudo-parity.
  • FIG. 6 shows detailed processing in the case of RAID5.
  • the disk drive 8-11 which receives write data to address #0 from the disk controller 7-1 via the interface 13-1:
  • the parity disk drive 8-1(n+1) which receives the pseudo-parity from the data disk drive 8-11 via the interface 14-1:
  • parity disks are not fixed in RAID5, when the write process is being executed for the disk drive 8-11 in which a request address (for example, #0) of the host computer exists and the disk drive 8-1(n+1) in which the parity data exists, access to address #(2n+1) of another disk drive 8-13 and the disk drive 8-12 in which the parity data exists is possible. Therefore, when the system is designed so that a parity update process on the parity interface and a data write/read process on the controller interface can be executed by a plurality of disk drives in parallel, the system performance can be further improved.
  • updating of parity data for writing data is executed via the interface between the disk drives after a disk drive sends an end report to the disk controller, so that the delay time due to a write penalty can be shortened viewed from the host computer.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Techniques For Improving Reliability Of Storages (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)
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Cited By (9)

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US6052822A (en) * 1997-12-22 2000-04-18 Electronics And Telecommunications Research Institute Fast destaging method using parity engine
US6161165A (en) * 1996-11-14 2000-12-12 Emc Corporation High performance data path with XOR on the fly
US6295587B1 (en) * 1999-09-03 2001-09-25 Emc Corporation Method and apparatus for multiple disk drive access in a multi-processor/multi-disk drive system
US6952797B1 (en) 2000-10-25 2005-10-04 Andy Kahn Block-appended checksums
US6976146B1 (en) 2002-05-21 2005-12-13 Network Appliance, Inc. System and method for emulating block appended checksums on storage devices by sector stealing
US20060075281A1 (en) * 2004-09-27 2006-04-06 Kimmel Jeffrey S Use of application-level context information to detect corrupted data in a storage system
US20080104444A1 (en) * 2006-10-05 2008-05-01 Hitachi Global Storage Technologies Netherlands B.V. System including a plurality of data storage devices connected via network and data storage device used therefor
US20110238885A1 (en) * 2009-05-25 2011-09-29 Hitachi, Ltd. Storage subsystem
US20150149819A1 (en) * 2013-11-27 2015-05-28 Electronics And Telecommunications Research Institute Parity chunk operating method and data server apparatus for supporting the same in distributed raid system

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JP3133004B2 (ja) * 1996-11-21 2001-02-05 株式会社日立製作所 ディスクアレイ装置およびその制御方法
JP3896206B2 (ja) * 1997-12-16 2007-03-22 インターナショナル・ビジネス・マシーンズ・コーポレーション Ｅｃｃブロック構造を使用する記憶装置のための符号化方法及びシステム
US6732201B2 (en) * 2001-12-17 2004-05-04 Lsi Logic Corporation Hardware speed selection behind a disk array controller
JP2003345513A (ja) * 2002-05-27 2003-12-05 Hitachi Ltd 記憶装置および記憶装置サブシステム
US7529967B2 (en) * 2004-11-04 2009-05-05 Rackable Systems Inc. Method and system for network storage device failure protection and recovery
JP5933755B2 (ja) 2012-04-27 2016-06-15 株式会社日立製作所 ストレージシステム及びストレージ制御装置
WO2013160972A1 (en) 2012-04-27 2013-10-31 Hitachi, Ltd. Storage system and storage apparatus
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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6161165A (en) * 1996-11-14 2000-12-12 Emc Corporation High performance data path with XOR on the fly
US6052822A (en) * 1997-12-22 2000-04-18 Electronics And Telecommunications Research Institute Fast destaging method using parity engine
US6295587B1 (en) * 1999-09-03 2001-09-25 Emc Corporation Method and apparatus for multiple disk drive access in a multi-processor/multi-disk drive system
US6530002B1 (en) * 1999-09-03 2003-03-04 Brian James Martin Method and apparatus for multiple disk drive access in a multi-processor/multi-disk drive system
US6952797B1 (en) 2000-10-25 2005-10-04 Andy Kahn Block-appended checksums
US6976146B1 (en) 2002-05-21 2005-12-13 Network Appliance, Inc. System and method for emulating block appended checksums on storage devices by sector stealing
US20060075281A1 (en) * 2004-09-27 2006-04-06 Kimmel Jeffrey S Use of application-level context information to detect corrupted data in a storage system
US20080104444A1 (en) * 2006-10-05 2008-05-01 Hitachi Global Storage Technologies Netherlands B.V. System including a plurality of data storage devices connected via network and data storage device used therefor
US8078921B2 (en) 2006-10-05 2011-12-13 Hitachi Global Storage Technologies Netherlands B.V. System including a plurality of data storage devices connected via network and data storage device used therefor
US20110238885A1 (en) * 2009-05-25 2011-09-29 Hitachi, Ltd. Storage subsystem
US8549381B2 (en) 2009-05-25 2013-10-01 Hitachi, Ltd. Storage subsystem
US8806300B2 (en) 2009-05-25 2014-08-12 Hitachi, Ltd. Storage subsystem
US20150149819A1 (en) * 2013-11-27 2015-05-28 Electronics And Telecommunications Research Institute Parity chunk operating method and data server apparatus for supporting the same in distributed raid system
US9411685B2 (en) * 2013-11-27 2016-08-09 Electronics And Telecommunications Research Institute Parity chunk operating method and data server apparatus for supporting the same in distributed raid system

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US5875460A (en) 1999-02-23
EP0701208B1 (de) 2004-03-17
EP1310875A3 (de) 2011-04-27
JP3661205B2 (ja) 2005-06-15
DE69532703D1 (de) 2004-04-22
EP0701208A2 (de) 1996-03-13
EP0701208A3 (de) 2001-08-16
DE69532703T2 (de) 2005-02-10
EP1310875A2 (de) 2003-05-14
JPH0876941A (ja) 1996-03-22

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